U.S. patent number RE39,759 [Application Number 10/836,859] was granted by the patent office on 2007-08-07 for time domain radio transmission system.
This patent grant is currently assigned to Time Domain Corporation. Invention is credited to Larry W. Fullerton.
United States Patent |
RE39,759 |
Fullerton |
August 7, 2007 |
Time domain radio transmission system
Abstract
A time domain communications system wherein a broadband of
time-spaced signals, essentially monocycle-like signals, are
derived from applying stepped-in-amplitude signals to a broadband
antenna, in this case, a reverse bicone antenna. When received, the
thus transmitted signals are multiplied by a D.C. replica of each
transmitted signal, and thereafter, they are, successively, short
time and long time integrated to achieve detection.
Inventors: |
Fullerton; Larry W.
(Brownsboro, AL) |
Assignee: |
Time Domain Corporation
(Huntsville, AL)
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Family
ID: |
27497942 |
Appl.
No.: |
10/836,859 |
Filed: |
April 30, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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07368831 |
Jun 20, 1989 |
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07192475 |
May 10, 1988 |
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06870177 |
Jun 3, 1986 |
4743906 |
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06677597 |
Dec 3, 1984 |
4641317 |
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Reissue of: |
07846597 |
Mar 5, 1992 |
05363108 |
Nov 8, 1994 |
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Current U.S.
Class: |
342/27; 342/21;
375/130; 375/256; 380/34 |
Current CPC
Class: |
G01S
7/282 (20130101); G01S 7/292 (20130101); G01S
13/0209 (20130101); G01S 13/18 (20130101); H01Q
9/28 (20130101); H01Q 21/061 (20130101); H04B
1/7174 (20130101); H04B 14/026 (20130101); H04B
1/71632 (20130101); H04B 1/71637 (20130101); H04B
1/719 (20130101); H04L 27/103 (20130101) |
Current International
Class: |
G01S
13/04 (20060101); H04L 27/30 (20060101) |
Field of
Search: |
;375/130-153,256 ;380/34
;342/21,22,27,28,118,120,127,132,134,145,201 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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2748746 |
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May 1978 |
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3542693 |
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Jun 1986 |
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581581 |
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Oct 1946 |
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GB |
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581811 |
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Oct 1946 |
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GB |
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4529445 |
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Sep 1970 |
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JP |
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51121389 |
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Oct 1976 |
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JP |
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58117741 |
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Jul 1983 |
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JP |
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593894 |
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Jan 1984 |
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JP |
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60035837 |
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Feb 1985 |
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JP |
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60093839 |
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May 1985 |
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JP |
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61136321 |
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Jun 1986 |
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JP |
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62024536 |
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Feb 1987 |
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JP |
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Primary Examiner: Gregory; Bernarr E.
Attorney, Agent or Firm: Venable LLP Babayi; Robert S.
Parent Case Text
This application is a continuation of application Ser. No.
07/368,831, filed on Jun. 20, 1989; which is a continuation-in-part
of application Ser. No. 07/192,475, filed on May 10, 1988; which is
a continuation-in-part of application Ser. No. 06/870,177, filed on
Jun. 3, 1986, now U.S. Pat. No. 4,743,906; which is a
continuation-in-part of application Ser. No. 06/677,597, filed on
Dec. 3, 1984, now U.S. Pat. No. 4,641,317.
.[.This application is also a continuation-in-part of International
Application No. PCT/US90/01174, filed on Mar. 2, 1990, which is a
continuation-in-part of International Application No.
PCT/US89/01020, filed on Mar. 10, 1989. Said PCT Application No.
PCT/US89/01020 is also a continuation-in-part of U.S. application
Ser. No. 07/010,440, filed on Feb. 3, 1987, now U.S. Pat. No.
4,813,057..].
Claims
I claim:
1. A wideband transmission system comprising: a transmitter
comprising: generating means for generating a plurality of time
spaced signals, each signal of said plurality of signals having a
stepped-in-amplitude portion; transmitting means including a broad
frequency band radiator responsive to said generating means for
transmitting wideband, time spaced, burst signals into a selected
medium; and receiving means responsive to wideband burst signals
present in said medium, as received signals, for processing said
received signals, by, (1) coherently detecting said received
signals, (2) integrating, separately, a plurality of coherently
detected signals, and (3) integrating the resultant plurality of
integrated signals and therefrom providing intelligence
signals.
2. A system as set forth in claim 1 wherein said system includes
reciprocal electrical-signal-to-sonic translation means and said
last-named means includes said broad frequency band radiator, and
said receiving means includes signal means responsive to said
reciprocal electrical-signal-to-sonic translation means and to said
times of initiation of said burst signals for coherently detecting
said signals.
3. A system as set forth in claim 2 wherein said medium is a
liquid.
4. A system as set forth in claim 1 wherein said medium is a
liquid.
5. A system as set forth in claim 1 wherein said broad frequency
band radiator comprises a broadband light radiator.
6. A system as set forth in claim 5 wherein said
broadband-frequency band radiator comprises: a laser; a light
modulator comprising: an elongated optical channel having an
entrance end for receiving light from said laser and a light
exiting end and having a refractive index variable by an electrical
field, and conductive means extending along said optical channel
for applying an electrical field to said optical channel; signal
means for generating a generally ramp-shaped voltage and applying
said voltage to said conductive means generally in the region of
said exiting end of said channel; and a dispersive medium disposed
to intercept the output of said channel and emit a responsive beam
which is characterized by a broad spectrum of light.
7. A system as set forth in claim 1 wherein said receiving means
includes template generating means for generating timed spaced
signals as template signals and multiplier means responsive to a
signal of said received signals and a template signal of said
template signals for providing an output, being a product signal,
and thereby coherently detecting the signal present during a said
template signal.
8. A system as set forth in claim 7 wherein said template
generating means generates said template signal at a time
subsequent to the transmitting of a burst signal of said burst
signals by said transmitting means.
9. A system as set forth in claim 7 wherein said template
generating means includes means for providing a variably delayable
template signal.
10. A system as set forth in claim 7 wherein: said template
generating means including for generating first and second said
template signals, said second template signal being delayed with
respect to said first template signal; said system includes first
and second said multiplier means, said first multiplier means being
responsive to a said received signal and said first template signal
for providing one said first product signal and second multiplier
means responsive to said second template signal and a said received
signal for providing another said product signal; first integrating
means responsive to said first product signal for integrating said
first product signal during the presence of said first template
signal and providing a first integrated signal; second integrating
means responsive to said second product signal for integrating said
second product signal during the presence of said second template
signal and providing a second integrated signal; and final
integrating and combining means responsive to said first and second
one integrated signals for combining and integrating said first and
second said integrated signals and providing intelligence signals
therefrom.
11. A system as set forth in claim 10 wherein integrating of said
first and second signals precedes combining.
12. A system as set forth in claim 7 wherein said template signal
is of a discrete polarity.
13. A system as set forth in claim 7 wherein said receiving means
includes: timing means responsive to the time of transmitting of
said burst signals for generating a set of said template signals,
each said template signal of said set of said template signals
being delayed by a like amount with respect to the transmitting of
a burst signal of said burst signals; and output means responsive
to said timing means and a set of resulting intelligence signals
for indicating the presence and distance of a target illuminated by
said burst signals at a range determined by said delayed said
amount.
14. A system as set forth in claim 13 wherein said receiving means
includes short time integrating means for, during the presence of
each said template signal of said set of template signals,
individually integrating each product signal from a said set as (2)
and including another integrating means for integrating the
resulting set of integrated product signals as (3).
15. A system as set forth in claim 7 wherein a said template signal
is generated responsive to a received signal of said received
signals.
16. A system as set forth in claim 1 wherein said transmitter
includes a source of potential, and switching means coupled to said
source and said radiator, and responsive to said signals from said
generating means, for abruptly changing the potential on said
radiator.
17. A system as set forth in claim 16 wherein said source of
potential is normally applied to said radiators and said switching
means reduces the potential on said radiator.
18. A system as set forth in claim 16 wherein: said switching means
comprises: a layer of normally high-resistance, but
light-responsive, low-resistance material, a pair of electrodes
coupled to said material, and said radiator has a pair of
terminals; said electrodes, said terminals,and said source of
potential are connected in series; and trigger means including a
light source and fiber optic, and responsive to said generating
means for applying a discrete increment of light from said light
source through said fiber optic to said layer of said material
wherein said material transitions from a high-resistance state to a
low-resistance state.
19. A system as set forth in claim 18 wherein said material is
diamond.
20. A system as set forth in claim 1 wherein said radiator
comprises a broadband dipole antenna having a pair of
triangular-shaped elements.
21. A system as set forth in claim 20 wherein said transmitter
includes a source of potential coupled to said dipole, and
switching means responsive to said generating means for abruptly
changing the potential on said dipole.
22. A system as set forth in claim 21 wherein said transmitting
means includes means for applying a switched source of potential to
said elements of said dipole antenna at points generally
intercepted by a line between the apices of said elements.
23. A system as set forth in claim 20 wherein said dipole antenna
is planar, and said system includes a plurality of like length
dipoles generally lying in a plane.
24. A system as set forth in claim 23 further comprising a
reflector positioned in a parallel plane to that of said plurality
of like length dipoles.
25. A system as set forth in claim 20 wherein said transmitter
includes: first and second electrical resistances; and power
switching means positioned adjacent to said dipole antenna and
being connected to one pole of said dipole through said first said
electrical resistance and connected to the other pole of said
dipole through said second resistance and responsive to a signal
from said generating means for abruptly changing the voltage across
poles of said broadband dipole antenna through said
resistances.
26. A system as set forth in claim 25 comprising: third and fourth
electrical resistances; a source of D.C. potential having first and
second terminals; a first terminal of said source of D.C. potential
being connected through said third resistance to one pole of said
dipole, and said second terminal of said source of D.C. potential
being connected through said fourth resistance to the other pole of
said dipole; and said power switching means includes means for
switching the state of D.C. potential on said dipole to a reduced
D.C. potential.
27. A system as set forth in claim 26 wherein said system includes
a coaxial cable through which said signals from said generating
means are supplied to said switching means.
28. A system as set forth in claim 27 wherein said source of
potential is applied through said coaxial cable to said dipole.
29. A system as set forth in claim 28 including constant current
means coupled through said coaxial cable and said dipole for
regulating current, charging current, to said dipole through said
third and fourth resistances.
30. A system as set forth in claim 1 wherein said time spaced
signals are varied in a time pattern.
31. A system as set forth in claim 30 wherein said time spaced
signals are a function of modulation.
32. A system as set forth in claim 1 further comprising: second and
third receiving means, the three said receiving means being spaced
apart; and combining means for combining intelligence signals from
said three receiving means and providing an indication of a target
illuminated by said transmitter and its direction.
33. A system as set forth in claim 1 wherein said receiving means
includes filter means responsive to said intelligence signals for
providing a signal responsive to a selected range of
frequencies.
34. A system as set forth in claim 1 wherein said receiving means
includes a dipole antenna comprising a pair of elements, each of
which, when viewed normal to the dipole length in at least one
plane, appears triangular, and wherein the bases of said elements
are parallel and and from which elements said received signals
appear.
Description
FIELD OF THE INVENTION
This invention relates generally to signal transmission systems,
and particularly to a time domain system wherein spaced narrow
signal bursts, impulses, or single cycles, or near single cycles
sometimes referred to as monocycles of electromagnetic energy
(radio or light) or sonic energy are transmitted in a compatible
medium and where signals have wideband frequency content and
wherein discrete frequency signal components are generally below
noise level and are thus not discernable by conventional receiving
equipment.
BACKGROUND OF THE INVENTION
Transmissions by radio, light, and sonic energy have heretofore
been largely approached from the point of view frequency content,
or band of frequencies. Thus, and with respect to radio, coexistent
different radio transmissions are permissible by means of
assignment of different frequencies or frequency channels to
different users, particularly those within the same geographic
area. Essentially foreign to this concept is that of tolerating
transmissions which are not frequency limited. While it would seem
that the very notion of not limiting frequency response would
create havoc with existing frequency denominated services, it has
been previously suggested that such is not necessarily true and
that, at least theoretically, it is possible to have overlapping
use of the radio spectrum. One suggested mode is that provided
wherein very short, on the order of one nanosecond or less, radio
pulses are applied to a broadband antenna which ideally would
respond by transmitting short burst signals, typically comprising
three to four polarity lobes, which comprise, energywise, signal
energy over essentially the upper entire band (above 100
megacycles) of the most frequently used radio frequency spectrum,
that is, up to the midgigahertz region. A basic discussion of
impulse effected radio transmission is contained in an article
entitled "Time Domain Electromagnetics and Its Application,"
Proceedings of the IEEE, Vol. 66, No. 3, March 1978. This article
particularly suggests the employment of such technology for
baseband radar, and ranges from 5 to 5,000 feet are suggested. As
noted, this article appeared in 1978, and now ten years later, it
is submitted that little has been accomplished by way of achieving
commercial application of this technology.
From both a theoretical and an experimental examination of the art,
it has become clear to the applicant that the lack of success have
largely been due to several factors. One is that the extremely wide
band of frequencies to be transmitted poses very substantial
requirements on an antenna. Antennas are generally designed for
limited frequency bandwidths, and traditionally when one made any
substantial change in frequency, it became necessary to choose a
different antenna or an antenna of different dimensions. This is
not to say that broadband antennas do not, in general, exist, but
in general, applicant is unaware of any prior practical structures
which, when excited by very short impulses, respond by the
transmission of burst signals as described above, the ideal for
this field of transmission. This view is based upon having tested
many antennas and from discussions with contemporaries who are
basically still struggling with the problem.
Two antenna types have received attention as being reasonably good
broadband radiators, or receivers--the bicone antenna and various
forms of horn antennas, particularly wherein the antenna becomes an
extension of a feed transmission line. The applicant has tested
published versions of both and has found that they simply fail to
meet the obvious goal of transmitting sufficiently short bursts.
Recently, applicant has learned of an improved horn-type antenna
with improved response. However, it is understood to be
three-dimensionally large and thus appears impractical for most
common uses.
A second problem which has plagued advocates of the employment of
impulse or time domain technology for radio is that of effectively
receiving and detecting the presence of the signal bursts,
particularly in the presence of high levels of existing ambient
radiation, present nearly everywhere. If one considers the problem
simply in terms of competition with the ambient signals, it might
appear insurmountable, and perhaps this is an explanation for the
lack of progress in receiver technology in this field. The state of
the art prior to applicant's entrance generally involved the
employment of brute force detection, that of threshold or time
threshold gate detection. Threshold detection simply enables
passage of signals higher than a selected threshold level. The
problem with this approach is obvious in that if one transmits
impulse generated signals which are of sufficient amplitude to rise
above ambient signal levels, the existing radio services producing
the latter may be unacceptably interferred with. For some reason,
perhaps because of bias produced by the wide spectrum of signal
involved, e.g., from 50 MHz on the order of 5 GHz, the possibility
of coherent detection has been thought impossible.
With respect to transmissions via light and sonic energy,
conventional techniques similarly call for relatively narrow
frequency band transmissions which require quite high spectral
density of frequency energy, and this in turn has been, in certain
applications, a disadvantage that can be detected by unintended
receivers.
Accordingly, it is the object of this invention to provide an
impulse or time domain (or baseband) transmission system which
attacks all of the above problems and to provide a complete impulse
time domain transmission system which, in the applicant's view,
eliminates the known practical barriers to its employment, and,
importantly, its employment for electromagnetic and sonic modes of
radio transmission, including communications, telemetry,
navigation, radar, and sonar.
SUMMARY OF THE INVENTION
With respect to radio signal transmissions, and as one aspect of
applicant's invention, a transmitting antenna is basically formed
quite opposite to the bicone antenna and wherein element
configuration is reversed, the two elements of the antenna each
being triangular in at least one X-Y dimension, and the bases of
these elements being positioned closely adjacent.
As a second aspect of the invention, a radio transmitter is a pulse
creating switching which is closely and directly connected to
antenna element, thus eliminating transmission line effects which
tend to undesirably lengthen the transmitted signal.
Third, by the combination of the applicant's antenna and
transmitter configurations, bursts, near monocyclic pulses, having,
for example, three to five polarity reversals, are transmitted and
received.
As a further consideration, practical power restraints in the past
have been generally limited to the application of a few hundred
volts of applied signal energy to the transmitting antenna. This
has been overcome by a transmitter switch which is formed by a
normally insulating crystalline structure, such as diamond material
sandwiched between two metallic electrodes, which are then closely
coupled to the elements of the antenna. This material is switched
to a conductive state by exciting it with an appropriate wavelength
beam of light, ultraviolet in the case of diamond. In this manner,
no metallic triggering communications line extends to the antenna
which might otherwise pick up radiation and re-radiate it,
adversely effecting signal coupling to the antenna and interfering
with the signal radiated from it, both of which tend to prolong the
length of a signal burst, a clearly adverse effect.
With respect to a radio receiver, as one aspect or feature of the
invention, a like receiving antenna is employed to that used for
transmission as described above. Second, a coordinately timed
signal to that of the transmitted signal is either detected from
the received signal, as in communications, dealt with in said U.S.
Pat. No. 4,979,186, or telemetry, or received directly from the
transmitter as, for example, in the case of radar. Then, the
coordinately timed signal, typically a simple half cycle of energy,
is mixed or multiplied with the received signal to determine
modulation or position of a target at a selected range, as the case
may be.
As still a further feature of this invention, transmitted burst
signals are varied in time pattern (in addition to a modulation
pattern for communications or telemetry). This greatly increases
the security of the system and differentiates signals from nearly,
if not all, ambient signals, that is, ambient signals which are not
synchronous with transmitted burst signals, an effect readily
achievable. This also enables the employment of faster repetition
rates with radar which would, absent such varying or dithering,
create range ambiguities as between returns from successive
transmission and therefore ranges. Burst signals are signals
generated when a stepped voltage change is applied to a broadband
antenna, such as a reverse bicone, but flat, antenna.
It is significant to note that here that bursts signals may be
generated, for example, by the application of a stepped voltage to
a broadband radiator.
As still a further feature of this invention, the repetition rate
of burst signals would be quite large, say, for example, up to 100
MHz, or higher, this enabling a very wide frequency dispersion, and
thus for a given overall power level, the energy at any one
frequency would be extremely small, thus effectively eliminating
the problem of interference with existing radio frequency based
services.
As still a further feature of this invention, moving targets are
detected in terms of their velocity by means of the employment of a
bandpass filter following mixing and double integration of signals.
As a still further feature of the invention when employed in this
latter mode, two channels of reception are ideally employed wherein
the incoming signal is multiplied by a selected range, or timed,
locally generated signal in one channel, and mixing the same
incoming signal by a slightly delayed, locally generated signal in
another channel, delay being on the order of 0.5 nanosecond. This
accomplishes target differentiation without employing a separate
series of transmissions.
As still another feature of this invention, multiple radiators or
receptors would be employed in an array wherein their combined
effect would be in terms of like or varied in time of sensed (or
transmitted) output and to thereby accent either a path normal to
the face of the antenna or to effect a steered path offset to a
normal path accomplished by selected signal delay paths.
As still another feature of this invention, radio antenna elements
would be positioned in front of a reflector wherein the distance
between the elements and reflector is in terms of the time of
transmission from an element or elements to reflector and back to
element(s), typically about three inches, this being with a
tip-to-tip dimension of elements of approximately nine inches.
As still another feature of the invention, wideband light, time
domain, transmissions are enabled and particularly by the
employment of a new and novel light frequency modulator.
Finally, and of very substantial significance, is that the light
modulator referred to the preceding paragraph provides what is
believed to be a breakthrough in conveniently enabling frequency
modulation of light signals passing, for example, through a fiber
optic having a variable refractive index with bias voltage.
Additionally, it may be employed as a selectable delay device.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an electrical block diagram illustrative of a basic radar
system constructed in accordance with this invention.
FIGS. 2 and 3 illustrate the configuration of a planar version of a
reverse bicone, but flat, antenna constructed as employed with this
invention.
FIGS. 4 and 5 diagrammatically illustrate an antenna array of
antennas as illustrated in FIGS. 2 and 3.
FIGS. 6-11 illustrate different switching assemblies as employed in
the charging and discharging of antennas to effect signal
transmission.
FIG. 12 illustrates a radar system particularly for employment in
facility surveillance, and FIG. 13 illustrates a modification of
this radar system.
FIGS. 14 and 15 illustrate the general arrangement of transmission
and receiving elements for three-dimensional location of
targets.
FIG. 16 is a schematic illustration of a modified portion of FIG. 1
illustrating transmission and reception of time domain type sonic
signals.
FIG. 17 is a schematic illustration of an alternate portion of FIG.
1 illustrating both the employment of light, time domain, signals
and a light modulation system adapted to produce broadband light
signals from the output of a conventional narrow band laser.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring to the drawings, FIG. 1 particularly illustrates a radar
application of the present invention for determining range.
Transmitting antenna 200 of transmitter 219 is a conformal reverse
bicone, but flat, antenna having triangular elements A and B with
closely spaced, 0,050 inches, bases. A dimension of an element
normal to the base is approximately 41/2 inches and is further
discussed and illustrated in FIGS. 2 and 3. Typically, a reflector
would be used as illustrated in FIG. 4.
The transmitter is basically controlled by control 210. It includes
a transmit sequence control portion 212 which determines the timing
of transmitted signal bursts, at, for example, 10,000 bursts per
second, in which case transmit sequence control 212 generates an
output at 10,000 Hz on lead 214. Oscillator 216 is operated at a
higher rate, for example, 20 MHz.
The signal output of transmit sequence control 212 is employed to
select particular pulse outputs of oscillator 216 to be the actual
pulse which is used as a master pulse for controlling both the
output of transmitter 218 and the timing of receiver functions, as
will be further described. In order to unambiguously and
repetitively select an operative pulse with low timing uncertainty
from oscillator 216, the selection is one and some fraction of an
oscillator pulse interval after an initial signal from control 212.
The selection is made via a control sequence employing D-type
flip-flops 218, 220, and 222. Thus, the transmit sequence control
pulse on lead 214 is applied to the clock input of flip-flop 218.
This causes the Q output of flip-flop 218 to transition to a high
state, and this is applied to a D input of flip-flop 220.
Subsequently, the output of oscillator 216 imposes a rising edge on
the clock input of flip-flop 220. At that time, the high level of
the D input of this flip-flop is transferred to the Q output.
Similarly, the Q output of flip-flop 220 is provided to the D input
of flip-flop 222, and the next rising edge of the pulse from
oscillator 216 will cause the not Q output of flip-flop 222 to go
low and thus initiate the beginning of the transmit-receive
cycle.
For the transmit mode, the not Q output of flip-flop 222 is fed as
an input to analog programmable delay 213 and to counter 215.
Counter 215, for example, would respond to the not Q outputs of
flip-flop 222 and count up to a selected number, for example, 256,
and recycle to count again. Its binary output would be fed as an
address to memory unit 217, ROM or RAM, which would have stored,
either in numerical address order, or randomly selected order, a
number. As a result, upon being addressed, a discrete output number
would be fed to D/A converter unit 221. D/A converter unit 221
would then provide an analog signal output proportional to the
input number. This output is employed to sequentially operate
programmable delay unit 213 for delays of pulses from flip-flop 222
by an amount proportional to the signal from D/A converter 221. The
range of delays or modulation would typically be up to the nominal
timing between pulses, in this case, up to 100 nanoseconds, and
practically up to 99 nanoseconds. The delayed output of
programmable delay unit 213 is then fed to fixed delay unit 224
which provides a fixed delay of 200 nanoseconds to each pulse that
it receives. The thus delayed pulses are then fed to trigger
generator 223. Trigger generator 223, e.g., an avalanche mode
operated transistor, would provide a sharply rising electrical
output at the 10,000 Hz rate or a like response of light output,
e.g., by laser, depending upon the transmitter to be driven. In
accordance with one feature of this invention, trigger generator
223 would be an ultraviolet laser, In any event, a pulse of trigger
generator 223 is fed to and rapidly turns on a switch 225 which,
for example, may again be an electrically operated or light
operated switch, such as a diamond switch in response to the
ultraviolet laser triggering device via fiber optic 227.
Importantly, it must be capable of switching in a period of a
nanosecond or less.
Conformal reverse bicone, but flat, antenna 200 is turned on or
turned off, or successively both, by switch assembly 215 which
applies stepped voltage changes to the antenna. It responds by
transmitting essentially short burst or monocycle signals 229 each
time that it is triggered. These burst signals are then transmitted
into space via a directional version of antenna 200 as illustrated
in FIGS. 4 and 5 or simply by an omnidirectional antenna as shown
by antenna 200 in FIG. 1.
Signal returns from a target would be received by receiver 226,
typically located near or together with transmitter 219, via
receiving antenna 202, again, a conformal reverse bicone antenna.
The received signals are amplified in amplifier 228 and fed to
mixer 230, together with a signal from template generator 232,
driven by delay line 236, which is timed to produce signals,
typically half cycles in configuration, and corresponding in time
to the anticipated time of arrival of a signal from a target at a
selected range.
Mixer 230 functions to multiply the two input signals, and where
there are coincidence signals, timewise and with like or unlike
polarity coincident signals, there is a significant and
integratable output. Since the goal here is to determine the
presence or absence of a target based on a number of signal
samplings as effected by integration, where a true target does not
exist, the appearance of signals received by mixer 230
corresponding to the time of receipt of signals from template
generator 232 will typically produce signals which vary not only in
amplitude but also in polarity. It is to be borne in mind that the
present system determines intelligence, not instantaneously, but
after a period of time, responsive to a preponderance of coherent
signals over time time, a facet of time domain transmissions. Next,
it is significant that the template generator produce a template
signal burst which is no longer than the effecting signal to be
received and bear a consistent like or opposite polarity
relationship in time with it. As suggested above, received signals
which do not bear this relation to the template signal will be
substantially attenuated. As one signal, the template signal is
simply a one polarity burst signal. Assuming that it maintains the
time relationship described, effective detection can be
effected.
For purposes of illustration, we are concerned with looking at a
single time slot for anticipated signal returns following signal
bursts from transmitting antenna 225. Accordingly, template
generator 232 is driven as a function of the timing of the
transmitter. To accomplish this, coarse delay counter 235 and fine
delay programmable delay line 236 are employed. Down counter 235
counts down the number of pulse outputs from oscillator 216 which
occur subsequent to a control input on lead 238, the output of
programmable delay unit 213. A discrete number of pulses thereafter
received from oscillator 216 is programmable in down counter 235 by
an output X from load counter 241 on lead 240 of control 210, a
conventional device wherein a binary count is generated in control
210 which is loaded into down counter 235. As an example, we will
assume that it is desired to look at a return which occurs 175
nanoseconds after the transmission of a signal from antenna 200. To
accomplish this, we load into down counter 235 the number "7,"
which means it will count seven of the pulse outputs of oscillator
216, each being spaced at 50 nanoseconds. So there is achieved a
350-nanosecond delay in down counter 235, but subtracting 200
nanoseconds as injected by delay unit 224, we will have really an
output of down counter 235 occurring 150 nanoseconds after the
transmission of a burst by transmitting antenna 200. In order to
obtain the precise timing of 175 nanoseconds, an additional delay
is effected by programmable delay line 236, which is triggered by
the output of down counter 235 when its seven count is concluded.
It is programmed in a conventional manner by load delay 242 of
control 210 on lead Y and, thus in the example described, would
have programmed programmable delay line 236 to delay an input pulse
provided to it by 25 nanoseconds. In this manner, programmable
delay line 236 provides a pulse output to template generator 232,
175 seconds after it is transmitted by bicone transmitting antenna
200. Template generator 232 is thus timed to provide, for example,
a positive half cycle or square wave pulse to mixer 230 or a
discrete sequence or pattern of positive and negative
excursions.
The output of mixer 230 is fed to analog integrator 250. Assuming
that there is a discrete net polarity likeness or unlikeness
between the template signal and received signal during the timed
presence of the template signal, analog integrator 250, which
effectively integrates over the period of template signal, will
provide a discrete voltage output. If the signal received is not
biased with a target signal imposed on it, it will generally
comprise as much positive content as negative content on a time
basis; and thus when multiplied with the template signal, the
product will follow this characteristic, and likewise, at the
output of integrator 250, there will be as many discrete products
which are positive as negative. On the other hand, with target
signal content, there will be a bias in one direction or the other,
that is, there will be more signal outputs of analog integrator 250
that are of one polarity than another. The signal output of analog
integrator 250 is amplified in amplifier 252 and then,
synchronously with the multiplication process, discrete signals
emanating from analog integrator 250 are discretely sampled and
held by sample and hold 254. These samples are then fed to A/D
converter 256 which digitizes each sample, effecting this after a
fixed delay of 40 microseconds provided by delay unit 258, which
takes into account the processing time required by sample and hold
unit 254. The now discrete, digitally calibrated positive and
negative signal values are fed from A/D converter 256 to digital
integrator 262 which then digitally sums them to determine whether
or not there is a significant net voltage of one polarity or
another, indicating, if such is the case, that a target is present
at a selected range. Typically, a number of transmissions would be
effected in sequence, for example, 10, 100, or even 1,000
transmissions, wherein the same signal transit time of reception
would be observed, and any signals occurring during like
transmissions would then be integrated in digital integrator 262,
and in this way enable recovery of signals from ambient,
non-synchronized signals which, because of random polarities, do
not effectively integrate.
The output of digital integrator 262 would be displayed on display
264, synchronized in time by an appropriate signal from delay line
236 (and delay 256) which would thus enable the time or distance
position of a signal return to be displayed in terms of distance
from the radar unit.
FIGS. 2 and 3 illustrate side and front views of a conformal
reverse bicone antenna 200. As is to be noted, antenna elements A
and B are triangular with closely adjacent bases and switch 225
connects close to the bases of the elements as shown. As an
example, and as described above, it has been found that good
quality burst signals can be radiated from impulses having a
stepped voltage change occurring in one nanosecond or less wherein
the base of each element is approximately 41/2 inches and the
height of each element is approximately the same.
FIGS. 4 and 5 diagrammatically illustrate an antenna assembly
wherein a multiple, in this case, 16, separate conformal reverse
bicone, but flat, antennas 200 are employed, each being spaced
forward of a metal reflector 200a by a distance of approximately
three inches, for a nine inch tip-to-tip antenna element dimension.
The antennas are supported by insulating standoffs 200b, and
switches 225 (transmitting mode) are shown to be fed by triggering
sources 223 which conveniently can be on the back side of reflector
200a, and thus any stray radiation which might tend to flow back
beyond this location to a transmission line is effectively
shielded. The multiple antennas may be operated in unison, that is,
all of them being triggered (in the case of a transmitter) and
combined (in the case of a receiver) with like timing, in which
case the antenna would have a view or path normal to the antenna
array or surface of reflector as a whole. Alternately, where it is
desired to effect beam steering, the timing by combination, or
triggering devices (receiving or transmitting) would be varied.
Thus, for example, with respect to reception, while the outputs of
all of the antennas in a column might be combined at a like time
point, outputs from other columns might be delayed before a final
combination of all signals. Delays can simply be determined by lead
lengths, and, in general, multiple effects are achievable in almost
limitless combinations.
FIG. 6 diagrammatically illustrates a transmitting switch wherein
the basic switching element is an avalanche mode operated
transistor 100, the emitter and collector of which are connected
through like resistors 102 to antenna elements A and B of conformal
reverse bicone antenna 200, the resistors being, for example, 25
ohms each. In the time between the triggering on of avalanche
transistor 100, it is charged to a D.C. voltage, e.g., 150 volts,
which is coordinate with the avalanche operating point of
transistor 100. Charging is effected from plus and minus supply
terminals through like resistors 104 to antenna elements A and B.
The primary of pulse transformer 108 is supplied a triggering
pulse, as from trigger circuit 223 of FIG. 1, and its secondary is
connected between the base and emitter of transistor 100.
Typically, the transmission line for the triggering pulse would be
in the form of a coaxial cable 110. When triggered on, transistor
100 shorts antenna elements A and B and produces a signal
transmission from antenna 200.
FIG. 7 illustrates a modified form of applying a charging voltage
to antenna elements A and B, in this case, via a constant current
source, and wherein the charging voltage is supplied across
capacitor 100 through coaxial cable 112, which also supplies a
triggering voltage to transformer 108, connected as described
above. For example, the plus voltage is supplied to the inner
conductor of coaxial cable 112, typically from a remote location
(not shown). This voltage is then coupled from the inner conductor
of the coaxial cable through the secondary of pulse transformer 108
and resistor 114, e.g., having a value of 1K ohms, to the collector
of a transistor 116 having the capability of standing the bias
voltage being applied to switching transistor 100 (e.g., 150
volts). The plus voltage is also applied through resistor 118, for
example, having a value of 220K ohms, to the base of transistor
116. A control circuit to effect constant current control is formed
by a zenar diode 120, across which is capacitor 122, this zenar
diode setting a selected voltage across it, for example, 71/2
volts. This voltage is then applied through a variable resistor 124
to the emitter of transistor 116 to set a constant voltage between
the base and emitter and thereby a constant current rate of flow
through the emitter-collector circuit of transistor 116, and thus
such to the antenna. Typically, it is set to effect a full voltage
charge on antenna 200 in approximately 90% of the time between
switch discharges by transistor 100. The thus regulated charging
current is fed through resistors 106 to antenna elements A and B.
In this case, discharge, matching, load resistors 102 are directly
connected between transistor 100 and antenna elements A and B as
shown.
FIG. 8 illustrates the employment of a light responsive element as
a switch, such as a light responsive avalanche transistor 124,
alternately a bulk semiconductor device, or a bulk crystalline
material such as diamond, would be employed as a switch, there
being switching terminals across, on opposite sides of, the bulk
material. The drive circuit would be similar to that shown in FIG.
6 except that instead of an electrical triggering system, a fiber
optic 126 would provide a light input to the light responsive
material, which would provide a fast change from high to low
resistance between terminals to effect switching.
FIG. 9 bears similarity to both FIGS. 7 and 8 in that it employs a
constant current power source with light responsive switching
element 124, such as a light responsive transistor, as shown. Since
there is no coaxial cable for bringing in triggering signals, other
means must be provided for bias voltage. In some applications, this
may simply be a battery with a D.C. to D.C. converter to provide
the desired high voltage source at plus and minus terminals.
FIGS. 10 and 11 illustrate the employment of multiple switching
elements, actually there being shown in each figure two avalanche
mode operated transistors 150 and 152 connected collector-emitter
in series with resistors 102 and antenna elements A and B. As will
be noted, separate transformer secondary windings of trigger
transformer 154 are employed to separately trigger the avalanche
mode transistors. The primary winding of a transformer would
typically be fed via a coaxial cable as particularly illustrated in
FIG. 6. Antenna elements A and B are charged between occurrences of
discharge from plus and minus supply terminals, as shown.
FIG. 9 additionally illustrates the employment of a constant
current source as described for the embodiment shown in FIGS. 6 and
7. Actually, the system of feeding the constant current source
through coaxial cable as shown in FIG. 5 can likewise be employed
with the circuitry shown in FIG. 11.
Referring to FIG. 12, there is illustrated a radar system
particularly intended for facility surveillance, and particularly
for the detection of moving targets, typically people. Transmitter
400 includes a 16 MHz clock signal which is generated by signal
generator 401. This signal is then fed to divide-by-16 divider 402
to provide output signals of 1 MHz. One of these 1 MHz outputs is
fed to 8-bit counter 404 which counts up to 256 and repeats. The
other 1 MHz output of divide-by-16 divider 402 is fed through a
programmable analog delay unit 406 wherein each pulse is delayed by
an amount proportional to an applied analog control signal. Analog
delay unit 406 is controlled by a magnitude of count from counter
404, which is converted to an analog voltage proportional to this
count by D/A converter 40p and applied to a control input of analog
delay unit 406.
By this arrangement, each of the 1 MHz pulses from divide-by-16
divider 402 is delayed a discrete amount. The pulse is then fed to
fixed delay unit 408 which, for example, delays each pulse by 60
nanoseconds in order to enable sufficient processing time of signal
returns by receiver 410. The output of fixed delay unit 408 is fed
to trigger generator 412, for example, an avalanche mode operated
transistor, which provides a fast rise time pulse. Its output is
applied to switch 414, typically an avalanche mode operated
transistor as illustrated in FIG. 6 or 7. Antenna 200, a conformal
reverse bicone antenna, is directly charged through resistors 104
from a capacitor 107 which generally holds a supply voltage
provided at the plus and minus terminals.
Considering now receiver 410, antenna 412, identical with antenna
200, receives signal returns and supplies them to mixer 414. Mixer
414 multiplies the received signals from antenna 412 with locally
generated ones from template generator 416. Template generator 416
is triggered via a delay chain circuitry of analog delay unit 406
and adjustable delay unit 418, which is set to achieve a generation
of a template signal at a time corresponding to the sum of delays
achieved by fixed delay 408 and elapsed time to and from a target
at a selected distance. The output of mixer 414 is fed to
short-term analog integrator 420 which discretely integrates for
the period of each template signal. Its output is then fed to
long-term integrator 422 which, for example, may be an active
low-pass filter and integrates over on the order of 50
milliseconds, or, in terms of signal transmissions, up to, for
example, approximately 50,000 such transmissions. The output of
integrator 422 is amplified in amplifier 424 and passed through
adjustable high-pass filter 426 to alarm 430. By this arrangement,
only A.C. signals corresponding to moving targets are passed
through the filters and with high-pass filter 426 establishing the
lower velocity limit for a target and low-pass filter 428
determining the higher velocity of a target. For example, high-pass
filter 426 might be set to pass targets moving at a greater
velocity than 0.1 feet per second and integrator-low-pass filter
422 adapted to pass signals representing targets moving less than
50 miles per hour. Assuming that the return signals pass both such
filters, alarm 430, which may be in any form of sensual indicator,
aural or visual, would be operated.
FIG. 13 illustrates a modification of FIG. 12 for the front-end
portion of receiver 410. As will be noted, there are two outputs of
antenna 200, one to each of separate mixers 450 and 452, mixer 450
being fed directly an output from template generator 418, and mixer
452 being fed an output from template generator 418 which is
delayed 0.5 nanosecond by 0.5 nanosecond delay unit 454. The
outputs of mixers 450 and 452 are then separately integrated in
short-term integrators 456 and 458, respectively. Thereafter, the
output of each of these short-term integrators is fed to separate
long-term integrators 460 and 462, after which their outputs are
combined in differential amplifier 464. The output of differential
amplifier 464 is then fed to high-pass filter 426 and then to alarm
430, as discussed above with respect to FIG. 12. Alternately, a
single long-term integrator may replace the two, being placed after
differential amplifier 464.
By this technique, there is achieved real time differentiation
between broad boundary objects, such as trees, and sharp boundary
objects, such as a person. Thus, assuming that in one instant the
composite return provides a discrete signal and later, for example,
half a nanosecond later, there was no change in the scene, then
there would be a constant difference in the outputs of mixers 450
and 452. However, in the event that a change occurred, as by
movement of a person, there would be changes in difference between
the signals occurring at the two different times, and thus there
would be a difference in the output of differential amplifier 464.
This output would then be fed to high-pass filter 426 (FIG. 12) and
would present a discrete change in the signal which would, assuming
that it met the requirements of high-pass and low-pass filters 426
and 428, be signalled by alarm 430.
In terms of a system as illustrated in FIG. 12, it has been able to
detect and discriminate very sensitively, sensing when there was a
moving object within the bounds of velocities described and within
the range of operation, several hundred feet or more. For example,
movement of an object within approximately a .+-. one-foot range of
a selected perimeter of measurement is examinable, leaving out
sensitivity at other distances which are neither critical nor
desirable in operation. In fact, this feature basically separates
the operation of this system from prior systems in general as it
alleviates their basic problem: committing false alarms. Thus, for
example, the present system may be positioned within a building and
set to detect movement within a circular perimeter within the
building through which an intruder must pass. The system would be
insensitive to passersby just outside the building. On the other
hand, if it is desirable to detect people approaching the building,
or, for that matter, approaching objects inside or outside the
building, then it is only necessary to set the range setting for
the perimeter of interest. In general, walls present no barrier. In
fact, in one test, an approximately four-foot thickness of stacked
paper was within the perimeter. In this test, movement of a person
just on the other side of this barrier at the perimeter was
detected.
While the operation thus described involves a single perimeter, by
a simple manual or automatic adjustment, observations at different
ranges can be accomplished. Ranges can be in terms of a circular
perimeter, or, as by the employment of a directional antenna
(antenna 200 with a reflector), effect observations at a discrete
arc.
FIG. 14 illustrates an application of applicant's radar to a
directional operation which might cover a circular area, for
example, from 20 to 30 feet to several thousand feet in radius. In
this illustration, it is assumed that there is positioned at a
selected central location a transmit conformal reverse bicone
antenna, in this case, oriented vertically as a non-directional, or
omnidirectional, antenna 300. There are then positioned at
120.degree. points around it like received antennas 302, 304, and
306. Antenna 300 is powered by a trigger switch transmitter.
Assuming that a single signal burst is transmitted from transmit
antenna 30, it would be radiated around 360.degree. and into space.
At some selected time as discussed above, receivers 308, 310,and
311 would be supplied a template signal as described above to thus,
in effect, cause the receivers to sample a signal echo being
received at that precise instant. This process would be repeated
for incrementally increasing or decreasing times, and thus there
would be stored in the memory's units 312, 314, and 316 signals
representative of a range of transit times. Then, by selection of a
combination of transit times for each of the receivers, in terms of
triangularizations, it is possible to select stored signals from
the memory units representative of a particular location in space.
For surveillance purposes, the result of signals derived from one
scan and a later occurring scan would be digitally subtracted, and
thus where an object at some point within the range of the unit has
moved to a new location, there will then be a difference in the
scan information. This thus would signal that something may have
entered the area. This process in general would be controlled by a
read-write control 318 which would control the memory's units 312,
314, and 316 and would control a comparator 320 which would receive
selected values X, Y, and Z from memory units 312, 314, and 316 to
make the subtraction. Display 322, such as an oscilloscope, may be
employed to display the relative position of an object change with
respect to a radar location.
FIG. 15 illustrates an application of applicant's invention to a
radar system wherein there is one transmitting antenna located in a
discrete plane position with respect to the direction of
observation, three receiving antennas spaced in a plane parallel to
the first plane, and a fourth receiving antenna positioned in a
third plane. Thus, radiation from transmitting antenna 404, which
is reflected by a target, is received by the four receiving
antennas at varying times by virtue of the difference in path
length. Because of the unique characteristic of applicant's system
in that it can be employed to resolve literally inches, extreme
detail can be resolved from the returns. Control 400 directs a
transmission by transmitter 402 which supplies a signal burst to
transmitting antenna 404. Signal returns are received by antennas
406, 408, and 410 and are located, for example, in a plane
generally normal to the direction of view and separate from the
plane in which transmit antenna 404 is located. A fourth receiving
antenna 412 is located in still a third plane which is normal to
the direction of view and thus in a plane separate from the plane
in which the other receiving antennas are located. By virtue of
this, there is provided means for locating, via triangularization,
a target in space, and thus there is derived sufficient signal
information to enable three-dimensional information displays. The
received signals from receivers 412, 414, 416, and 418 are
separately supplied to signal processor and comparator 420, which
includes a memory for storing all samples received and in terms of
their time of receipt. From this data, one can compute position
information by an appropriate comparison as well as target
characteristics, such as size and reflectivity, and displayed by
display 422.
FIG. 16 illustrates a portion of a radar system generally shown in
FIG. 1 except that the pulse output of switch 235 is applied
through an impedance matching device, i.e., resistor 500, to
wideband sonic transducer 502. Sonic transducer 502 is a known
structure, it being, for example, constructed of a thin
piezoelectric film 504 on opposite sides of which are coated
metallic films 506 and 508 as electrodes. The energizing pulse is
applied across these plates. Impedance matching is typically
required as switch 235 would typically supply a voltage from a
relatively low impedance source whereas sonic transducer 502
typically would have a significantly higher impedance. The sonic
output of sonic transducer 502, a wide frequency band, on the order
of at last three octaves, would typically be attached to an
impedance transformer for the type of medium into which the sonic
signal is to be radiated, for example, transducer 502 would attach
to a law impedance material 503, such as glass, in turn mounnted on
a support 505 (for example, the hull of a ship).
An echo or reflection from a target of the signal transmitted by
sonic transducer 502 would be received by a similarly configured
sonic transducer 520, and its output would then be coupled via
plates 512 and 514 to amplifier 228 and thence onto mixer 230 as
illustrated in FIG. 1 wherein operation would be as previously
described.
FIG. 17 illustrates a broadband light transmitter. Thus, a pulse
from switch 225 (FIG. 1) triggers a conventional laser 522
operating, for example, in a conventional narrow frequency mode at
approximately 700 nanometers to provide such an output to a narrow
band to wideband light converter assembly consisting of light
modulator 524 and a dispersive medium 526. The output of laser 522
is applied to one end 528 of a fiber optic 523 having a variable
refractive index with respect to an applied voltage and, in this
case, for example, having a thickness dimension on the order of 2
millimeters and a length dimension of approximately 1 meter. The
fiber optic is positioned between two elongated metallic or
otherwise conductive plates 530 and 532. A modulating voltage from
signal generator 534, for example, a ramp voltage, as shown as
applied across the plates adjacent the exiting end of fiber optic
523. Generator 534 typically would be triggered also by switch 225
to create, in this example, a ramp voltage which would effect a
traveling wave from right to left along the plates and thus along
the enclosed fiber optic, opposing the traveling light pulse from
left to right. As a result, there is effected a light output at end
536 which varies, changing from the initial wavelength of the input
light pulse to a higher or lower frequency, and this, in effect,
creates a chirp-type pulse. It is then supplied to a dispersive
material 526 such as lead glass, with the result that at its
output, the resultant light pulse is converted to a quite short
duration pulse having a wide broadband spectrum of frequencies, or
white or near white light output. Emitted beam 538 then travels
outward and upon striking a target, a reflection is reflected back
to optical mixer 540 which is also supplied a laser output pulse
from laser 542, in turn triggered by delay line 236. As a result,
optical mixer 540 multiplies the two input signals and provides an
electrical output to analog integrator 250 after which the signal
is processed as generally described with respect to FIG. 1.
It is believed of perhaps greater significance that light modulator
524, a frequency modulator, described above has many other
applications, and particularly as an intelligence modulator of a
laser beam. In such case, the laser input would typically be
supplied in a continuous or spaced input, and the modulating
waveform would be whatever was desired to mix with or impress on
the laser beam.
* * * * *
References